JPH08277762A - Accumulator type fuel injection system - Google Patents

Abstract

PURPOSE: To reduce fuel consumption and also, to materialize vibration reduction, noise reduction, and NOx reduction of exhaust gas by constituting an accumulation means, which reserves pressured fuel, out of the first accumulator and the second accumulator which reserves fuel at lower pressure than the fuel pressure within the first accumulator, and selectively connecting each accumulator. CONSTITUTION: At the time of nonoperation of a fuel injection nozzle 10, a controller 66 demagnetizes the second three-dimensional solenoid valve 86, and low-pressure fuel within the second accumulator 78 is supplied to a fuel reservoir 14. Likewise, the first three-dimensional solenoid valve 34 is demagnetized, too, and high-pressure fuel in the first accumulator 36 is supplied to an oil chamber 26. When the first three-dimensional solenoid valve 34 is energized at fuel injection in this condition, the fuel pressure within the oil chamber 26 is removed, and a nozzle needle 18 opens, and performs pilot injection. Successively, when the second three-dimensional solenoid valve 86 is energized and high-pressure fuel within the first accumulator 36 is supplied into the fuel reservoir 14, the first three-dimensional solenoid valve 34 is energized again, and the nozzle needle 18 opens and performs main injection.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure accumulation type fuel injection device.

[0002]

2. Description of the Related Art A typical structure of a conventional pressure-accumulation fuel injection for a diesel engine will be described with reference to the schematic structure diagram of FIG. In the figure, reference numeral 10 generally indicates a fuel injection nozzle,
The injection nozzle 10 has a nozzle 16 having a plurality of fuel injection holes 12 formed at the tip thereof and a fuel reservoir 14 for storing the fuel supplied to the injection holes 12.

Inside the nozzle 16, the fuel reservoir 14 and the injection hole 1 are provided.
A nozzle needle 18 for controlling communication with the nozzle 2 is slidably accommodated, and the nozzle needle 18 is constantly urged in a closing direction by a pressure spring 24 via a push rod 22 stored in a nozzle holder 20. . An oil chamber 26 is formed in the nozzle holder 20.
Inside, the nozzle needle 18 and the push rod 22
On the other hand, a hydraulic piston 28 is coaxially and slidably fitted.

The oil chamber 26 is connected to a first outlet b of a three-way solenoid valve 34 via a one-way valve 30 and an orifice 32 which are arranged in parallel, and the solenoid valve 34 is further connected to the pressure accumulator 3.
6 which is in communication with the fuel tank 38
It is equipped with an exit C. The outlet b is selectively connected to the inlet a or the second outlet c by the valve body 42 driven by the electromagnetic actuator 40, and when the electromagnetic actuator 40 is deenergized, the inlet a is the first outlet b. When the electromagnetic actuator 40 is energized, the first outlet b communicates with the second outlet c. In addition, the nozzle holder 20 and the nozzle 16
A feed hole 44 that connects the fuel reservoir 14 to the pressure accumulator 36 is provided therein.

The pressure accumulator 36 is supplied with fuel of a high pressure preset according to the operating state of the engine by a fuel pressurizing pump generally indicated by the reference numeral 46. The fuel pressurizing pump 46 includes a plunger 50 that is reciprocally driven by an eccentric wheel or a cam 48 that is driven in conjunction with the crankshaft of the engine. The plunger 50 is placed in a pump chamber 54 by a low-pressure feed pump 52. The supplied oil in the fuel tank 38 is pressurized and pressure-fed to the pressure accumulator 36 via the one-way valve 56.

Between the discharge side passage 58 of the pump chamber 54 and the suction side passage 60 communicating with the feed pump 52,
Spill valve 6 opened and closed by electromagnetic actuator 62
4, the electromagnetic actuator 62 and the electromagnetic actuator 40 of the three-way electromagnetic valve 34 are controlled by a controller 66, respectively.

The controller 66 detects a cylinder discriminating device 68 for discriminating individual cylinders of a multi-cylinder engine, an engine speed and crank angle detecting device 70, an engine load detecting device 72, and fuel pressure in the pressure accumulator 36. The fuel pressure sensor 74 and, if necessary, the auxiliary information 76 such as the temperature, the atmospheric pressure, and the fuel temperature that influence the operating state of the engine are received, and the electromagnetic actuators 40 and 6 are received.
Control 2

The operation mode of the conventional pressure-accumulation type fuel injection device will be briefly described as follows. First, an eccentric wheel or cam 48 that is driven in conjunction with the crankshaft of the engine
The plunger 50 is driven by the feed pump 52.
The low-pressure fuel supplied to the pump chamber 54 is pressurized to a high pressure and supplied to the pressure accumulator 36.

According to the operating state of the engine, a drive output is supplied from the controller 66 to the electromagnetic actuator 62 to open / close the spill valve 64, and the spill valve 64 causes the fuel pressure in the pressure accumulator 36 to be a preset high pressure. (For example, 800 to 1000 atm). On the other hand, a signal indicating the fuel pressure in the pressure accumulator 36 is fed back from the sensor 74 to the controller 66.

The high-pressure fuel in the pressure accumulator 36 is supplied to the fuel reservoir 14 via the feed hole 44 of the fuel injection nozzle 10 and presses the nozzle needle 18 upward, that is, in the opening direction. On the other hand, when the fuel injection nozzle 10 is inoperative, the electromagnetic actuator 40 of the three-way electromagnetic valve 34 is deenergized and the inlet a and the first outlet b are in communication, so the pressure accumulator 3
The high-pressure fuel 6 is supplied to the oil chamber 26 via the one-way valve 30 and the orifice 32.

The hydraulic piston 28 in the oil chamber 26 is pressed downward by the fuel pressure in the oil chamber 26, and the valve closing force obtained by adding the pressing force based on this oil pressure to the spring force of the pressure spring 24 is the push rod. It is applied to the nozzle needle 18 via 22. The pressure receiving area of the fuel pressure acting downward on the hydraulic piston 28 is set sufficiently larger than the acting area of the fuel pressure acting upward on the nozzle needle 18, and the downward spring force of the pressure spring 24 additionally acts. Nozzle needle 1
8 is held in the closed position shown.

Next, when the electromagnetic actuator 40 is energized by the drive output of the controller 66, the inlet a and the first
The communication with the outlet b is blocked, and the first outlet b and the second outlet c
And are communicated. For this reason, the oil chamber 26 is connected to the fuel tank 38 via the orifice 32 and the second outlet c, the fuel pressure acting on the hydraulic piston 28 is removed, and the pressure spring 24 acts on the nozzle needle 18 to direct the upward fuel. Overcome by pressure and the same nozzle needle 1
8 is opened, and the high pressure fuel in the fuel reservoir 14 is injected from the injection holes 12 into the cylinder.

After a preset time according to the operating state of the engine, the electromagnetic actuator 40 is de-energized by the controller 66, the inlet a of the three-way electromagnetic valve 34 and the first outlet b are communicated again, and the hydraulic piston 28 is connected. Since the fuel pressure in the pressure accumulator 36 is applied, the nozzle needle 18 is closed and the fuel injection is completed.

Since the pressure-accumulation fuel injection device can supply the high pressure fuel of the set pressure stored in the pressure accumulator 36 to each cylinder of the engine, the rotational speed fluctuates over a wide range from idle operation to high speed full power operation. However, there is a general advantage that high performance can be secured in the entire operating range of the vehicle diesel engine that operates in the load region.

However, in a normal fuel injection device,
Since fuel is supplied at one time by opening the set time of the nozzle needle 18, the heat generation rate dQ / dθ is plotted on the ordinate and the crank angle θ (or time) is plotted on the abscissa. As shown by the curve Q _o in the typical heat generation pattern diagram, in the early stage of combustion, high-temperature and high-pressure abrupt explosion combustion is performed, and the engine operating noise increases, and NO _x in the exhaust gas increases. There are increasing defects.

In order to reduce the above-mentioned operating noise and NO _x in the exhaust gas, the fuel injection rate dq / dθ is plotted on the vertical axis and the crank angle θ (or time) is plotted on the horizontal axis. As shown by the curve I in the injection rate diagram, a small amount (for example, about 10% of the total injection amount) of the pilot injection I _p is initially performed in each short time θ ₁ for each fuel injection cycle, and then stopped. It is known that it is effective to adopt an injection pattern in which the main injection I _m with a large amount of the remaining amount is carried out over a relatively long time θ ₃ after the time θ ₂ .

That is, when the above-described two-stage fuel injection pattern is adopted, the small amount of fuel initially pilot-injected does not immediately burn, but causes mild combustion together with the fuel injected early in the subsequent main-injection. As shown by the curve Q ₁ in the heat generation pattern diagram of _No. 4, combustion with a relatively low maximum pressure and temperature occurs, thus reducing the vibration and noise of the engine, and reducing NO _x in the exhaust gas. There is an advantage that the amount is small.

Therefore, it is expected that an improvement in engine performance and a reduction in vibration noise and NO _x can be achieved at the same time by combining the above-mentioned pressure accumulation type fuel injection device and the above-mentioned two-stage fuel injection pattern. In a conventional fuel injection device that handles high-pressure fuel of around 1000 atm, no matter how quickly the Ξ solenoid valve 34 is energized and deenergized, the responsiveness of the hydraulic system is not sufficient, so the injection time is short. That is, it is actually extremely difficult to realize the injection pattern as shown in (θ ₁ + θ ₂ + θ ₃ ) of FIG.

[0019]

SUMMARY OF THE INVENTION The present invention was devised in view of the above circumstances, and it is possible to enjoy the advantages of two-stage fuel injection while maintaining the advantages of the pressure-accumulation fuel injection device.
Therefore, in order to realize a diesel engine especially for a vehicle, which has excellent performances such as output and fuel efficiency, low vibration noise, and low NO _{x in} exhaust gas, the first high pressure fuel is stored. It is an object of the present invention to provide a fuel injection device including a pressure accumulator and a control unit that regulates the fuel pressure to a second pressure accumulator that stores fuel having a pressure lower than that of the first accumulator. .

[0020]

To achieve the above object, the present invention provides a fuel pressure accumulating means for accumulating pressurized fuel, and a fuel supplying means for supplying pressurized fuel to the fuel accumulating means. A fuel injection nozzle having a nozzle needle for controlling fuel injection by opening and closing thereof, and closing the nozzle needle by applying a fuel pressure from the fuel pressure accumulating means to the nozzle needle and removing the fuel pressure. In a fuel injection device including fuel injection control means for opening a nozzle needle, the pressure accumulating means stores a first pressure accumulator and a second pressure accumulator for accumulating fuel having a pressure lower than the fuel pressure in the first pressure accumulator. With and
Fuel pressure switching means for selectively communicating the fuel reservoir in the fuel injection nozzle with the first pressure accumulator or the second pressure accumulator, and operation of the fuel injection control means and the fuel pressure switching means during fuel injection. The fuel supply means includes a first control pressure means for adjusting the supply pressure of the fuel supplied to the pressure accumulating means, and between the first pressure control means and the second pressure accumulator. It is an object of the present invention to propose a pressure-accumulation type fuel injection device characterized by comprising a second pressure control means provided to adjust the fuel pressure in the second pressure accumulator.

In the present invention, there are provided first and second pressure sensors for detecting the fuel pressures in the first and second pressure accumulators, respectively, and the controller responds to the outputs of the first and second pressure sensors. It is preferable that the operation of the first and second pressure control means be controlled so that the fuel pressures in the first and second pressure accumulators become predetermined set pressures. Further, it is preferable that the controller controls the operation of the second pressure control means so that the fuel pressure in the second pressure accumulator becomes a preset substantially constant pressure.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION A preferred embodiment of the present invention will be specifically described below with reference to FIG. (Note that members and parts that are substantially the same as or corresponding to those of the conventional device described with reference to FIG. 2 are denoted by the same reference numerals, and redundant description will be omitted.) As illustrated, according to the present invention For example, in addition to the first pressure accumulator 36 that stores high-pressure (for example, 800 to 1000 atm) fuel corresponding to the conventional pressure accumulator, a relatively low pressure (for example, 300
A second pressure accumulator 78 is provided for storing fuel of up to 500 atm.

The second pressure accumulator 78 is connected to the fuel pressurizing pump 46 via an oil passage 80, and an electromagnetic opening / closing valve 82 is provided in the oil passage 80. The electromagnetic opening / closing valve 82 is opened / closed by the drive output supplied from the controller 66 according to the operating state of the engine, and adjusts the fuel pressure in the second pressure accumulator 78 to the set pressure. For the sake of simplicity, the set fuel pressure in the second pressure accumulator 78 may be a constant pressure, for example 300 atm, regardless of the operating state of the engine. Also,
The second pressure accumulator 78 has a pressure sensor 8 for detecting the fuel pressure.
4 is provided, and the output signal of the sensor 84 is supplied to the controller 66.

On the other hand, in addition to the conventional three-way solenoid valve for controlling the fuel pressure supplied to the hydraulic piston 28, that is, the first three-way solenoid valve 34, the fuel injection nozzle 10 is generally denoted by reference numeral 86. A second three-way solenoid valve is provided.

The second three-way solenoid valve 86 is provided in the first pressure accumulator 36.
One of the first inlet X connected to the upstream feed hole 44a communicating with the second inlet z connected to the second pressure accumulator 78 is connected to the downstream feed hole 44 communicating with the fuel reservoir 14.
a valve element 88 selectively connected to the outlet y connected to b;
Electromagnetic actuator 90 for switching and operating the valve body 88
It consists of and. The electromagnetic actuator 90 is controlled by the drive output of the controller 66.

The mode of operation of the above device is as follows.
First, when the fuel injection nozzle 10 is inoperative, the electromagnetic actuator 90 of the second three-way electromagnetic valve 86 is deenergized by the controller 66, the second inlet z and the outlet y are communicated with each other, and the inside of the second pressure accumulator 78 is provided. Is supplied to the fuel reservoir 14. On the other hand, the electromagnetic actuator 40 of the first three-way electromagnetic valve 34 is deenergized, the inlet a and the first outlet b are communicated, and the high pressure fuel of the first pressure accumulator 36 is supplied to the oil chamber 26. Therefore, the nozzle needle 18 is kept closed in the manner described in detail for the conventional fuel injection nozzle.

Next, at the time of fuel injection, the controller 66
As a result, the electromagnetic actuator 40 of the first three-way electromagnetic valve 34 is energized, the first outlet b and the second outlet c are communicated, and the fuel pressure in the oil chamber 26 is removed. As a result, the pressure spring 24 is overcome, the nozzle needle 18 is opened, the low-pressure fuel in the fuel reservoir 14 is injected from the injection hole 12 into the cylinder, and the pilot injection shown by I _p in FIG. 3 is performed.

The electromagnetic actuator 40 of the first three-way solenoid valve 34 is deenergized by the controller 66 after a very short time, that is, after a lapse of the crank angle θ1 and after an actual moment, the first accumulator is again stored in the oil chamber 26. The high-pressure fuel in 36 is supplied, the nozzle needle 18 is closed, and the pilot injection I _p is stopped.

Next, during the crank angle θ2 of FIG. 3, the controller 66 urges the electromagnetic actuator 90 of the second three-way electromagnetic valve 86 to communicate the first inlet X and the outlet y, and the fuel sump 14 is reached. The high-pressure fuel in the first pressure accumulator 36 is supplied. Subsequently, the electromagnetic actuator 40 of the first three-way electromagnetic valve 34 is the nozzle needle 18 is opened as described above is biased by the controller 66, high pressure fuel is injected into the cylinder main injection I _m is performed. After a time corresponding to the crank angle θ ₃ , the electromagnetic actuator 40 is deenergized by the controller 66, the nozzle needle 18 is closed, and one injection cycle including the pilot injection I _p and the main injection I _m is completed.

Since the gentle combustion is performed by the two-stage injection consisting of the pilot injection I _p and the main injection I _m , the operating noise and vibration of the engine are reduced and at the same time,
There is an advantage that NO _x in the exhaust gas is reduced, and at the same time, the main injection I _m is performed by the high pressure fuel, so that combustion can be improved and engine performance can be improved. Further, according to the above configuration, the opening and closing of the nozzle needle is performed by the first three-way solenoid valve 34, and the fuel switching between the pilot injection I _p and the main injection I _m is performed by the second three-way solenoid valve 8.
Since it is performed by No. 6, the responsiveness is excellent, and the two-stage injection of the desired pattern can be reliably performed. It should be noted that in the above-described embodiment, the first chamber is provided in the oil chamber 26 via the three-way solenoid valve 34.
The fuel pressure in the pressure accumulator 36 is supplied, but the fuel pressure in the second pressure accumulator 78 can be changed to be supplied in the oil chamber 26. In this case, the three-way solenoid valve is used. The inlet a of 38 may be connected to the second pressure accumulator 78 instead of the first pressure accumulator 36.

[0031]

As described above, the pressure-accumulation type fuel injection device according to the present invention has a fuel pressure accumulating means for accumulating the pressurized fuel and a fuel supply for supplying the pressurized fuel to the fuel accumulating means. Means and a fuel injection nozzle having a nozzle needle for controlling fuel injection by opening and closing the means, and closing the nozzle needle by applying fuel pressure from the fuel pressure accumulating means to the nozzle needle and removing the fuel pressure. A fuel injection control means for opening the nozzle needle by means of the first pressure accumulator and a second pressure accumulator for accumulating fuel at a pressure lower than the fuel pressure in the first pressure accumulator. With a pressure accumulator,
Fuel pressure switching means for selectively communicating the fuel reservoir in the fuel injection nozzle with the first pressure accumulator or the second pressure accumulator, and operation of the fuel injection control means and the fuel pressure switching means during fuel injection. And a fuel pressure control means for adjusting the supply pressure of the fuel supplied to the pressure accumulating means, and between the first pressure controlling means and the second pressure accumulator. A second pressure control means provided to adjust the fuel pressure in the second pressure accumulator is provided, and the advantage of the two-stage fuel injection is enjoyed while maintaining the advantages of the pressure accumulation type fuel injection device. In order to realize a diesel engine especially for a vehicle, which is excellent in performance such as output and fuel efficiency, has low vibration noise, and has low NO _{x in} exhaust gas, the pressurized high pressure fuel is stored. First to do There is an advantage that it is possible to provide a fuel injection device that includes a pressure accumulator and a control unit that adjusts the fuel pressure for the second pressure accumulator that stores fuel at a pressure lower than the fuel pressure of the second accumulator.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a conventional pressure accumulation type fuel injection device.

3 is a diagram showing a fuel injection pattern in the injection device shown in FIG. 1. FIG.

4 is a diagram showing a heat generation pattern corresponding to the fuel injection pattern shown in FIG.

FIG. 5 is a diagram showing a heat generation pattern when normal fuel injection is performed.

[Explanation of symbols]

10 ... Fuel injection nozzle, 12 ... Injection hole, 14 ... Fuel sump, 1
8 ... Nozzle needle, 28 ... Hydraulic piston, 34 ... First
Three-way solenoid valve, 36 ... First pressure accumulator, 46 ... Fuel pressure pump, 66 ... Controller, 78 ... Second pressure accumulator, 86 ... Second three-way solenoid valve.

Claims (3)

[Claims] 1. A fuel injection means having a fuel pressure accumulating means for accumulating pressurized fuel, a fuel supply means for supplying the pressurized fuel to the fuel accumulating means, and a nozzle needle for controlling fuel injection by opening and closing thereof. Fuel injection including a nozzle and fuel injection control means for closing the nozzle needle by applying a fuel pressure from the fuel pressure accumulating means to the nozzle needle and opening the nozzle needle by removing the fuel pressure In the device, the pressure accumulating means has a first pressure accumulator and a second pressure accumulator for accumulating fuel having a pressure lower than the fuel pressure in the first pressure accumulator, and the fuel accumulator in the fuel injection nozzle and the fuel accumulator in the fuel injection nozzle. Fuel pressure switching means for selectively communicating with the first pressure accumulator or the second pressure accumulator, and operation of the fuel injection control means and the fuel pressure switching means during fuel injection The fuel supply means adjusts the supply pressure of the fuel supplied to the pressure accumulating means, and between the first pressure control means and the second pressure accumulator. A pressure-accumulation fuel injection device, comprising: a second pressure control means provided to adjust the fuel pressure in the second pressure accumulator. 2. A first pressure sensor and a second pressure sensor for respectively detecting fuel pressures in the first and second pressure accumulators, wherein the controller controls the first pressure sensor according to the outputs of the first pressure sensor and the second pressure sensor. The pressure-accumulation fuel injection device according to claim 1, wherein the operations of the first and second pressure control means are controlled so that the fuel pressures in the first and second pressure accumulators respectively become predetermined set pressures. 3. The controller controls the operation of the second pressure control means so that the fuel pressure in the second pressure accumulator becomes a preset substantially constant pressure. ACCUMULATION TYPE FUEL INJECTION DEVICE